Question

Solve for r and t: 6r - 3t = 6 6r + 8t = -16

Answer 1

Multiply the first equation with (-1)
you should get this

-6r + 3t = -6
6r + 8t = -16

start to eliminate

11t = -22

divide by 11

t = -2

substitute 

6r - 3(-2) = 6
6r + 6 = 6
6r = 6 - 6
6r = 0 
r=0